Carbon stocks and sequestration potentials of agricultural soils in the federal state of Baden-Wurttemberg, SW Germany

Soil organic carbon (SOC) inventories are important tools for studying the effects of land-use and climate change and evaluating climate-change policies. A detailed inventory of SOC in the agricultural soils of the federal state of Baden-Wurttemberg was therefore prepared based on the highest-resolution geo-referenced soil, land-use, and climate data (BUK200 inventory). In order to estimate the quality of different approaches, C inventories of the region were also prepared based on data from the National Inventory Report (UBA, 2003) and by applying the IPCC (1997) method to the two data sets. Finally, the BUK200 inventory was used to estimate potentials of no-tillage agriculture (NT) and peatland restoration to contribute to C sequestration and greenhouse-gas (GHG)-emission mitigation since both measures are discussed in this context. Scenario assumptions were change to NT on 40% of the cropland and restoration of 50% of cultivated peatlands within 20 years. On average, grasslands contained 9.5 kg C m(-2) to 0.3 m depth as compared to only 6.0 kg C m(-2) under cropland, indicating strong land-use effects. The SOC content depended strongly on waterlogging and elevation, thus reflecting reduced C mineralization under aquic moisture regimes and low temperatures. Comparison of the BUK200 inventory with the approach used for UBA (2003) showed high inconsistencies due to map resolution and SOC contents, whereas the IPCC method led to fairly good agreements. Results on the simulated effects of NT and peatland restoration suggested that 5%-14% of total agricultural GHG emissions could be abated with NT whereas peat restoration appeared to have a minor mitigation potential (0.2%-2.7%) because the total area of cultivated organic soils was too small to have larger impact.